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September 11, 2008

Pfizer: Withdraws Zeven Marketing Applications

by Sam Savage

Healthcare giant Pfizer has announced that the marketing applications for its skin infection treatment Zeven (dalbavancin) are to be withdrawn, pending another multi-center trial for the drug. This setback could cost Pfizer dearly: another trial could push the drug's launch date out to September 2010, five full years after its proposed launch date and just two years before its first patent expiry.

Pfizer's decision to invest in another Phase III trial for Zeven will have been painful. There has been a substantial delay since the FDA's second approvable letter, issued in December 2007, in which the regulator requested additional non-inferiority data. Pfizer will undoubtedly have been looking for ways to provide this through novel cuts of existing trial data, but it seems that the company has seen an additional trial as the only way to satisfy the FDA's request.

Perhaps the most significant drawback for Pfizer is the potential time lag implied by further trials, which could run to another two years (based on the time taken for Versicor to run a relatively small 150 patient trial to supplement the drug's original two core Phase III trials, combined with an additional FDA review period). However, the opportunity costs of the drug not being on the market extend beyond lost revenues during this period.

Combined with delays in gaining approval to date, this setback will further erode the drug's patented life. The original molecule patent expires in 2012, and, following the drug's guaranteed five years of exclusivity post-launch, process and dosage patents are likely to be eagerly contested by the generics industry. However, it may be protected by a manufacturing process patent until 2017 and a novel dosage patent which Versicor secured in 2005.

This additional delay will disadvantage Zeven in an era where skin and soft tissue infection prescriptions are being hotly contested by currently marketed products (e.g. AstraZeneca's Merrem, Cubist's Cubicin and Pfizer's Zyvox), in the run up to new competition from Astellas (Arbelic), Johnson & Johnson (Zeftera), Arpida (iclaprim) and Targanta (Nuvocid). Pfizer already has a key competitor on the market in the form of Zyvox, and Astellas and Johnson & Johnson have also faced regulatory delays with their own treatments (Arebelic and Zeftera). However, this may be little consolation for Pfizer, should new market entrants gain a stronger foothold during Zeven's extended development.